1. Field
The present invention relates to an accelerator device which outputs a signal indicating a rotation angle of a rotary body to be rotated by external operation for controlling opening and the like of a throttle valve.
2. Description of the Related Art
Traditionally, an accelerator device and a throttle valve are interlocked by a wire (an outer tube and an inner wire), for example. Recently, fuel injection apparatuses have been used instead of carburetors. In such a case, an operational amount of an accelerator device is measured, the measured operational amount is output as a signal, opening of a throttle valve and a fuel injection amount in a fuel injection apparatus are controlled based on the signal, and further, the signal is used for controlling an automatic transmission.
Here, a portion of an accelerator device to be operated by an operator has a similar structure to the traditional one even though a wire is not used. For example, an accelerator pedal similar to the traditional one is used for an automobile in which an accelerator device is operated with a foot and an accelerator grip is used for a vehicle or the like such as a motorcycle in which an accelerator device is operated with a hand.
A rotary body is rotated with operation of the accelerator pedal or the accelerator grip, a rotation angle of the rotary body is measured, and a signal based on the measured rotation angle is defined as the signal indicating the abovementioned operational amount.
Further, an accelerator pedal and an accelerator grip are operated toward an acceleration side (a side to enlarge opening of a throttle valve) from an idling position and urged to be returned from an operational position at the acceleration side toward the idling position by return urging means.
Accordingly, when operating the accelerator pedal or the accelerator grip, an operator performs operation to the acceleration side against the return urging means and performs operation to the idling side with urging force of the return urging means or as suppressing the urging force thereof.
Traditionally, owing to that an outer tube and an inner wire is connected to an accelerator device, friction force of the inner wire sliding against the outer tube is applied in addition to urging force of the abovementioned return urging means. Accordingly, the urging force of the return urging means is determined in consideration of the friction force of the inner wire. Further, traditionally, the abovementioned friction force of the inner wire generates hysteresis between rotation toward an acceleration side and rotation toward a returning side in relation between a rotation angle of a rotary body and rotation torque of the rotary body. Here, torque required to rotate the rotary body toward the acceleration side is higher than that toward the returning side at the same rotation angle of the rotary body.
The hysteresis stabilizes operability of small acceleration operation. Here, with an accelerator device which simply outputs a signal without having an inner wire being connected, an operator develops a feeling of strangeness with influence to operability as being different from traditional operability. Accordingly, it has been desired to stabilize operability.
In view of the above, it has been proposed to generate the above-mentioned hysteresis by generating friction corresponding to urging force of return urging means at a section rotated with accelerator operation. For example, see Japanese Patent Publication No. 3602295.
In Japanese Patent Publication No. 3602295, an accelerator shaft is rotatably supported about an axis via a bearing with a bearing bush arranged at a housing. An accelerator lever which is rotated in accordance with accelerator pedal operation is rotatably fixed to the accelerator shaft as being integrated therewith. A sensor measures a rotation angle of the accelerator shaft and outputs a signal indicating the rotation angle, for example, for controlling opening of a throttle valve.
An outer spring and an inner spring being torsion coil springs are coaxially arranged in a two-track manner around the accelerator shaft.
Further, an outer spring guide is arranged as being rotatable integrally with the accelerator lever and movable slightly in a decentering direction (a direction intersecting with a circumferential direction) and is provided with a cylindrical guide portion inserted to the outer spring.
Further, an inner spring guide having a guide portion to which the inner spring is inserted is arranged as being rotatable integrally with the outer spring guide and movable slightly in the decentering direction.
The outer spring is fixed respectively to the outer spring guide and the housing and urges the accelerator lever via the outer spring guide in a rotation direction being an accelerator closing direction (a direction to close the throttle valve).
The inner spring is fixed respectively to the inner spring guide and the housing and urges the accelerator lever in the accelerator closing direction via the inner spring guide and the outer spring guide. Further, the inner spring is arranged between the inner spring guide and the housing in a state of being compressed in the axial direction. Further, the inner spring guide is slightly movable in the axial direction of the accelerator shaft.
Further, a support including an approximately cylindrical outer guide wall capable of contacting to an inner circumferential face of the guide portion of the outer spring guide and an approximately cylindrical inner guide wall capable of contacting to an inner circumferential face of the guide portion of the inner spring guide is attached to the housing. Further, the support is slightly movable in the axial direction of the accelerator shaft.
In the accelerator device as described above, when the accelerator lever is to be rotated with accelerator operation in an accelerator opening direction (a direction to open the throttle valve), urging force of the outer spring and the inner spring is exerted in the opposed rotation direction.
At that time, the outer spring exerts force to move the outer spring guide in the decentering direction, so that friction force is generated with an inner circumferential face of the guide portion of the outer spring guide pressed to the outer circumferential face of the outer guide wall of the support.
Further, the inner spring exerts force to move the inner spring guide in the decentering direction, so that friction force is generated with an inner circumferential face of the guide portion of the inner spring guide pressed to an outer circumferential face of the inner guide wall of the support.
Further, since the inner spring is arranged between the inner spring guide and the housing in a compressed state, urging force is generated in the axial direction (rotation axis direction) of the accelerator shaft. Accordingly, the inner spring guide is pressed to the support along the rotation axis direction and the support is pressed to the spring guide thereby. Thus, when the inner spring guide and the outer spring guide are rotated along with the accelerator lever, friction force is generated between the inner spring guide and the support and between the support and the outer spring.
In the accelerator device, the abovementioned hysteresis can be generated owing to the abovementioned friction between the inner spring guide and the support and between the outer spring guide and the support instead of friction between an inner wire and an outer tube which are conventionally used.
In Japanese Patent Publication No. 3602295, since the force of the outer spring and the inner spring to decenter the outer spring guide and the inner spring guide is small and the friction force caused thereby is small, two springs being the outer spring and the inner spring are inevitably required. Further, owing to that the inner spring is arranged in a state of being compressed in the axial direction to supplement friction force with the decentering, friction force in the rotation axis direction is used as well as the decentering direction.
In Japanese Patent Publication No. 3602295 described above, since a number of members such as the outer spring, the outer spring guide, the support having two-track cylindrical guide walls, the inner spring, and inner spring guide are required to be arranged approximately coaxially, the accelerator device becomes large in the spring radial direction and miniaturization becomes difficult.
Further, since the inner spring is accommodated in a compressed state, loads are exerted in the axial direction of the accelerator shaft on the housing and a fastening portion for fixing such as a fixing portion of the accelerator lever to cause structural problems.
Further, since the outer spring guide and the inner spring guide are movable in the decentering direction against the outer guide wall and the inner guide wall of the support, there is a clearance between the guide portion of the outer spring guide and the outer guide wall and there is a clearance between the guide portion of the inner spring guide and the inner guide wall.
The outer spring guide and the inner spring guide are moved by the abovementioned force in the decentering direction based on the clearances, so that the guide portion of the outer spring guide and the outer spring guide are to be contacted and the guide portion of the inner spring guide and the inner guide wall are to be contacted. Further, in accordance with a rotation angle of the accelerator lever, the abovementioned decentering direction is varied and the abovementioned contact position is varied as well.
In such a state, there is a fear of entering of foreign matters into the abovementioned clearances. In a case that foreign matters enter to be sandwiched or to be further bitten between members, for example, there is a problem that the accelerator device is in a state of poor operation and operational failure.
Two hooks of the outer spring and two hooks of the inner spring are engaged with the housing and either of the outer spring guide and the inner spring guide. Here, for matching force exerted by the outer spring and the inner spring in the decentering direction, positions of the hooks of the outer spring and the inner spring are required to be matched. Accordingly, restriction occurs for return force and angles of the springs and designing of the accelerator device is restricted.
Further, the decentering direction of the two springs is not always stabled. Further, for obtaining large force with the springs in the decentering direction, it is required that a wire diameter of the torsion coil spring is enlarged and that effective turns are lessened.
Further, for finely adjusting hysteresis difference, it is required to vary a spring hook position or to vary spring characteristics (return force, thrust force). In such a case, it is required to match the decentering directions of the two springs as described above, so that difficult adjustment is caused.
Further, in Japanese Patent Publication No. 3602295, the support is to be contacted to each of the outer spring guide and the inner spring guide respectively at two positions in the decentering direction and the rotation direction, so that friction force is generated at four contact positions in total. Further, the friction force is balanced with accuracy in shape of each member. In addition, the direction of the friction force is varied in accordance with the rotation angle of the accelerator lever, as described above. In such a state, there is a fear that a plurality of steps in torque characteristics of the accelerator lever is caused by wear of each member due to friction. In such a case, since the torque characteristics are varied, for example, there is a fear that a feeling of strangeness occurs at operability.